#define JPEG_INTERNALS
#define AM_MEMORY_MANAGER	/* we define jvirt_Xarray_control structs */
#include "jinclude.h"
#include "jpeglib.h"
#include "jmemsys.h"		/* import the system-dependent declarations */

#ifndef NO_GETENV
#ifndef HAVE_STDLIB_H		/* <stdlib.h> should declare getenv() */
extern char * getenv JPP( ( const char * name ) );
#endif
#endif


/*
   Some important notes:
     The allocation routines provided here must never return NULL.
     They should exit to error_exit if unsuccessful.

     It's not a good idea to try to merge the sarray and barray routines,
     even though they are textually almost the same, because samples are
     usually stored as bytes while coefficients are shorts or ints.  Thus,
     in machines where byte pointers have a different representation from
     word pointers, the resulting machine code could not be the same.
*/


/*
   Many machines require storage alignment: longs must start on 4-byte
   boundaries, doubles on 8-byte boundaries, etc.  On such machines, malloc()
   always returns pointers that are multiples of the worst-case alignment
   requirement, and we had better do so too.
   There isn't any really portable way to determine the worst-case alignment
   requirement.  This module assumes that the alignment requirement is
   multiples of sizeof(ALIGN_TYPE).
   By default, we define ALIGN_TYPE as double.  This is necessary on some
   workstations (where doubles really do need 8-byte alignment) and will work
   fine on nearly everything.  If your machine has lesser alignment needs,
   you can save a few bytes by making ALIGN_TYPE smaller.
   The only place I know of where this will NOT work is certain Macintosh
   680x0 compilers that define double as a 10-byte IEEE extended float.
   Doing 10-byte alignment is counterproductive because longwords won't be
   aligned well.  Put "#define ALIGN_TYPE long" in jconfig.h if you have
   such a compiler.
*/

#ifndef ALIGN_TYPE		/* so can override from jconfig.h */
#define ALIGN_TYPE  double
#endif


/*
   We allocate objects from "pools", where each pool is gotten with a single
   request to jpeg_get_small() or jpeg_get_large().  There is no per-object
   overhead within a pool, except for alignment padding.  Each pool has a
   header with a link to the next pool of the same class.
   Small and large pool headers are identical except that the latter's
   link pointer must be FAR on 80x86 machines.
   Notice that the "real" header fields are union'ed with a dummy ALIGN_TYPE
   field.  This forces the compiler to make SIZEOF(small_pool_hdr) a multiple
   of the alignment requirement of ALIGN_TYPE.
*/

typedef union small_pool_struct * small_pool_ptr;

typedef union small_pool_struct {
  struct {
    small_pool_ptr next;	/* next in list of pools */
    size_t bytes_used;		/* how many bytes already used within pool */
    size_t bytes_left;		/* bytes still available in this pool */
  } hdr;
  ALIGN_TYPE dummy;		/* included in union to ensure alignment */
} small_pool_hdr;

typedef union large_pool_struct FAR * large_pool_ptr;

typedef union large_pool_struct {
  struct {
    large_pool_ptr next;	/* next in list of pools */
    size_t bytes_used;		/* how many bytes already used within pool */
    size_t bytes_left;		/* bytes still available in this pool */
  } hdr;
  ALIGN_TYPE dummy;		/* included in union to ensure alignment */
} large_pool_hdr;


/*
   Here is the full definition of a memory manager object.
*/

typedef struct {
  struct jpeg_memory_mgr pub;	/* public fields */

  /* Each pool identifier (lifetime class) names a linked list of pools. */
  small_pool_ptr small_list[JPOOL_NUMPOOLS];
  large_pool_ptr large_list[JPOOL_NUMPOOLS];

  /* Since we only have one lifetime class of virtual arrays, only one
     linked list is necessary (for each datatype).  Note that the virtual
     array control blocks being linked together are actually stored somewhere
     in the small-pool list.
  */
  jvirt_sarray_ptr virt_sarray_list;
  jvirt_barray_ptr virt_barray_list;

  /* This counts total space obtained from jpeg_get_small/large */
  long total_space_allocated;

  /* alloc_sarray and alloc_barray set this value for use by virtual
     array routines.
  */
  JDIMENSION last_rowsperchunk;	/* from most recent alloc_sarray/barray */
} my_memory_mgr;

typedef my_memory_mgr * my_mem_ptr;


/*
   The control blocks for virtual arrays.
   Note that these blocks are allocated in the "small" pool area.
   System-dependent info for the associated backing store (if any) is hidden
   inside the backing_store_info struct.
*/

struct jvirt_sarray_control {
  JSAMPARRAY mem_buffer;	/* => the in-memory buffer */
  JDIMENSION rows_in_array;	/* total virtual array height */
  JDIMENSION samplesperrow;	/* width of array (and of memory buffer) */
  JDIMENSION maxaccess;		/* max rows accessed by access_virt_sarray */
  JDIMENSION rows_in_mem;	/* height of memory buffer */
  JDIMENSION rowsperchunk;	/* allocation chunk size in mem_buffer */
  JDIMENSION cur_start_row;	/* first logical row # in the buffer */
  JDIMENSION first_undef_row;	/* row # of first uninitialized row */
  wxjpeg_boolean pre_zero;		/* pre-zero mode requested? */
  wxjpeg_boolean dirty;		/* do current buffer contents need written? */
  wxjpeg_boolean b_s_open;		/* is backing-store data valid? */
  jvirt_sarray_ptr next;	/* link to next virtual sarray control block */
  backing_store_info b_s_info;	/* System-dependent control info */
};

struct jvirt_barray_control {
  JBLOCKARRAY mem_buffer;	/* => the in-memory buffer */
  JDIMENSION rows_in_array;	/* total virtual array height */
  JDIMENSION blocksperrow;	/* width of array (and of memory buffer) */
  JDIMENSION maxaccess;		/* max rows accessed by access_virt_barray */
  JDIMENSION rows_in_mem;	/* height of memory buffer */
  JDIMENSION rowsperchunk;	/* allocation chunk size in mem_buffer */
  JDIMENSION cur_start_row;	/* first logical row # in the buffer */
  JDIMENSION first_undef_row;	/* row # of first uninitialized row */
  wxjpeg_boolean pre_zero;		/* pre-zero mode requested? */
  wxjpeg_boolean dirty;		/* do current buffer contents need written? */
  wxjpeg_boolean b_s_open;		/* is backing-store data valid? */
  jvirt_barray_ptr next;	/* link to next virtual barray control block */
  backing_store_info b_s_info;	/* System-dependent control info */
};


#ifdef MEM_STATS		/* optional extra stuff for statistics */

LOCAL( void )
print_mem_stats( j_common_ptr cinfo, int pool_id ) {
  my_mem_ptr mem = ( my_mem_ptr ) cinfo->mem;
  small_pool_ptr shdr_ptr;
  large_pool_ptr lhdr_ptr;
  /* Since this is only a debugging stub, we can cheat a little by using
     fprintf directly rather than going through the trace message code.
     This is helpful because message parm array can't handle longs.
  */
  fprintf( stderr, "Freeing pool %d, total space = %ld\n",
           pool_id, mem->total_space_allocated );
  for( lhdr_ptr = mem->large_list[pool_id]; lhdr_ptr != NULL;
       lhdr_ptr = lhdr_ptr->hdr.next ) {
    fprintf( stderr, "  Large chunk used %ld\n",
             ( long ) lhdr_ptr->hdr.bytes_used );
  }
  for( shdr_ptr = mem->small_list[pool_id]; shdr_ptr != NULL;
       shdr_ptr = shdr_ptr->hdr.next ) {
    fprintf( stderr, "  Small chunk used %ld free %ld\n",
             ( long ) shdr_ptr->hdr.bytes_used,
             ( long ) shdr_ptr->hdr.bytes_left );
  }
}

#endif /* MEM_STATS */

static void out_of_memory( j_common_ptr cinfo, int which ) {
  #ifdef MEM_STATS
  cinfo->err->trace_level = 2;	/* force self_destruct to report stats */
  #endif
  ERREXIT1( cinfo, JERR_OUT_OF_MEMORY, which );
}


static const size_t first_pool_slop[JPOOL_NUMPOOLS] = {
  1600,			/* first PERMANENT pool */
  16000			/* first IMAGE pool */
};

static const size_t extra_pool_slop[JPOOL_NUMPOOLS] = {
  0,			/* additional PERMANENT pools */
  5000			/* additional IMAGE pools */
};

#define MIN_SLOP  50		/* greater than 0 to avoid futile looping */


METHODDEF( void * )
alloc_small( j_common_ptr cinfo, int pool_id, size_t sizeofobject )
/* Allocate a "small" object */
{
  my_mem_ptr mem = ( my_mem_ptr ) cinfo->mem;
  small_pool_ptr hdr_ptr, prev_hdr_ptr;
  char * data_ptr;
  size_t odd_bytes, min_request, slop;
  /* Check for unsatisfiable request (do now to ensure no overflow below) */
  if( sizeofobject > ( size_t )( MAX_ALLOC_CHUNK - SIZEOF( small_pool_hdr ) ) )
  { out_of_memory( cinfo, 1 ); }	/* request exceeds malloc's ability */
  /* Round up the requested size to a multiple of SIZEOF(ALIGN_TYPE) */
  odd_bytes = sizeofobject % SIZEOF( ALIGN_TYPE );
  if( odd_bytes > 0 )
  { sizeofobject += SIZEOF( ALIGN_TYPE ) - odd_bytes; }
  /* See if space is available in any existing pool */
  if( pool_id < 0 || pool_id >= JPOOL_NUMPOOLS )
  { ERREXIT1( cinfo, JERR_BAD_POOL_ID, pool_id ); }	/* safety check */
  prev_hdr_ptr = NULL;
  hdr_ptr = mem->small_list[pool_id];
  while( hdr_ptr != NULL ) {
    if( hdr_ptr->hdr.bytes_left >= sizeofobject )
    { break; }			/* found pool with enough space */
    prev_hdr_ptr = hdr_ptr;
    hdr_ptr = hdr_ptr->hdr.next;
  }
  /* Time to make a new pool? */
  if( hdr_ptr == NULL ) {
    /* min_request is what we need now, slop is what will be leftover */
    min_request = sizeofobject + SIZEOF( small_pool_hdr );
    if( prev_hdr_ptr == NULL )	/* first pool in class? */
    { slop = first_pool_slop[pool_id]; }
    else
    { slop = extra_pool_slop[pool_id]; }
    /* Don't ask for more than MAX_ALLOC_CHUNK */
    if( slop > ( size_t )( MAX_ALLOC_CHUNK - min_request ) )
    { slop = ( size_t )( MAX_ALLOC_CHUNK - min_request ); }
    /* Try to get space, if fail reduce slop and try again */
    for( ;; ) {
      hdr_ptr = ( small_pool_ptr ) jpeg_get_small( cinfo, min_request + slop );
      if( hdr_ptr != NULL )
      { break; }
      slop /= 2;
      if( slop < MIN_SLOP )	/* give up when it gets real small */
      { out_of_memory( cinfo, 2 ); } /* jpeg_get_small failed */
    }
    mem->total_space_allocated += min_request + slop;
    /* Success, initialize the new pool header and add to end of list */
    hdr_ptr->hdr.next = NULL;
    hdr_ptr->hdr.bytes_used = 0;
    hdr_ptr->hdr.bytes_left = sizeofobject + slop;
    if( prev_hdr_ptr == NULL )	/* first pool in class? */
    { mem->small_list[pool_id] = hdr_ptr; }
    else
    { prev_hdr_ptr->hdr.next = hdr_ptr; }
  }
  /* OK, allocate the object from the current pool */
  data_ptr = ( char * )( hdr_ptr + 1 ); /* point to first data byte in pool */
  data_ptr += hdr_ptr->hdr.bytes_used; /* point to place for object */
  hdr_ptr->hdr.bytes_used += sizeofobject;
  hdr_ptr->hdr.bytes_left -= sizeofobject;
  return ( void * ) data_ptr;
}


/*
   Allocation of "large" objects.

   The external semantics of these are the same as "small" objects,
   except that FAR pointers are used on 80x86.  However the pool
   management heuristics are quite different.  We assume that each
   request is large enough that it may as well be passed directly to
   jpeg_get_large; the pool management just links everything together
   so that we can free it all on demand.
   Note: the major use of "large" objects is in JSAMPARRAY and JBLOCKARRAY
   structures.  The routines that create these structures (see below)
   deliberately bunch rows together to ensure a large request size.
*/

METHODDEF( void FAR * )
alloc_large( j_common_ptr cinfo, int pool_id, size_t sizeofobject )
/* Allocate a "large" object */
{
  my_mem_ptr mem = ( my_mem_ptr ) cinfo->mem;
  large_pool_ptr hdr_ptr;
  size_t odd_bytes;
  /* Check for unsatisfiable request (do now to ensure no overflow below) */
  if( sizeofobject > ( size_t )( MAX_ALLOC_CHUNK - SIZEOF( large_pool_hdr ) ) )
  { out_of_memory( cinfo, 3 ); }	/* request exceeds malloc's ability */
  /* Round up the requested size to a multiple of SIZEOF(ALIGN_TYPE) */
  odd_bytes = sizeofobject % SIZEOF( ALIGN_TYPE );
  if( odd_bytes > 0 )
  { sizeofobject += SIZEOF( ALIGN_TYPE ) - odd_bytes; }
  /* Always make a new pool */
  if( pool_id < 0 || pool_id >= JPOOL_NUMPOOLS )
  { ERREXIT1( cinfo, JERR_BAD_POOL_ID, pool_id ); }	/* safety check */
  hdr_ptr = ( large_pool_ptr ) jpeg_get_large( cinfo, sizeofobject +
            SIZEOF( large_pool_hdr ) );
  if( hdr_ptr == NULL )
  { out_of_memory( cinfo, 4 ); }	/* jpeg_get_large failed */
  mem->total_space_allocated += sizeofobject + SIZEOF( large_pool_hdr );
  /* Success, initialize the new pool header and add to list */
  hdr_ptr->hdr.next = mem->large_list[pool_id];
  /* We maintain space counts in each pool header for statistical purposes,
     even though they are not needed for allocation.
  */
  hdr_ptr->hdr.bytes_used = sizeofobject;
  hdr_ptr->hdr.bytes_left = 0;
  mem->large_list[pool_id] = hdr_ptr;
  return ( void FAR * )( hdr_ptr + 1 ); /* point to first data byte in pool */
}


/*
   Creation of 2-D sample arrays.
   The pointers are in near heap, the samples themselves in FAR heap.

   To minimize allocation overhead and to allow I/O of large contiguous
   blocks, we allocate the sample rows in groups of as many rows as possible
   without exceeding MAX_ALLOC_CHUNK total bytes per allocation request.
   NB: the virtual array control routines, later in this file, know about
   this chunking of rows.  The rowsperchunk value is left in the mem manager
   object so that it can be saved away if this sarray is the workspace for
   a virtual array.
*/

METHODDEF( JSAMPARRAY )
alloc_sarray( j_common_ptr cinfo, int pool_id,
              JDIMENSION samplesperrow, JDIMENSION numrows )
/* Allocate a 2-D sample array */
{
  my_mem_ptr mem = ( my_mem_ptr ) cinfo->mem;
  JSAMPARRAY result;
  JSAMPROW workspace;
  JDIMENSION rowsperchunk, currow, i;
  long ltemp;
  /* Calculate max # of rows allowed in one allocation chunk */
  ltemp = ( MAX_ALLOC_CHUNK - SIZEOF( large_pool_hdr ) ) /
          ( ( long ) samplesperrow * SIZEOF( JSAMPLE ) );
  if( ltemp <= 0 )
  { ERREXIT( cinfo, JERR_WIDTH_OVERFLOW ); }
  if( ltemp < ( long ) numrows )
  { rowsperchunk = ( JDIMENSION ) ltemp; }
  else
  { rowsperchunk = numrows; }
  mem->last_rowsperchunk = rowsperchunk;
  /* Get space for row pointers (small object) */
  result = ( JSAMPARRAY ) alloc_small( cinfo, pool_id,
                                       ( size_t )( numrows * SIZEOF( JSAMPROW ) ) );
  /* Get the rows themselves (large objects) */
  currow = 0;
  while( currow < numrows ) {
    rowsperchunk = MIN( rowsperchunk, numrows - currow );
    workspace = ( JSAMPROW ) alloc_large( cinfo, pool_id,
                                          ( size_t )( ( size_t ) rowsperchunk * ( size_t ) samplesperrow
                                              * SIZEOF( JSAMPLE ) ) );
    for( i = rowsperchunk; i > 0; i-- ) {
      result[currow++] = workspace;
      workspace += samplesperrow;
    }
  }
  return result;
}


/*
   Creation of 2-D coefficient-block arrays.
   This is essentially the same as the code for sample arrays, above.
*/

METHODDEF( JBLOCKARRAY )
alloc_barray( j_common_ptr cinfo, int pool_id,
              JDIMENSION blocksperrow, JDIMENSION numrows )
/* Allocate a 2-D coefficient-block array */
{
  my_mem_ptr mem = ( my_mem_ptr ) cinfo->mem;
  JBLOCKARRAY result;
  JBLOCKROW workspace;
  JDIMENSION rowsperchunk, currow, i;
  long ltemp;
  /* Calculate max # of rows allowed in one allocation chunk */
  ltemp = ( MAX_ALLOC_CHUNK - SIZEOF( large_pool_hdr ) ) /
          ( ( long ) blocksperrow * SIZEOF( JBLOCK ) );
  if( ltemp <= 0 )
  { ERREXIT( cinfo, JERR_WIDTH_OVERFLOW ); }
  if( ltemp < ( long ) numrows )
  { rowsperchunk = ( JDIMENSION ) ltemp; }
  else
  { rowsperchunk = numrows; }
  mem->last_rowsperchunk = rowsperchunk;
  /* Get space for row pointers (small object) */
  result = ( JBLOCKARRAY ) alloc_small( cinfo, pool_id,
                                        ( size_t )( numrows * SIZEOF( JBLOCKROW ) ) );
  /* Get the rows themselves (large objects) */
  currow = 0;
  while( currow < numrows ) {
    rowsperchunk = MIN( rowsperchunk, numrows - currow );
    workspace = ( JBLOCKROW ) alloc_large( cinfo, pool_id,
                                           ( size_t )( ( size_t ) rowsperchunk * ( size_t ) blocksperrow
                                               * SIZEOF( JBLOCK ) ) );
    for( i = rowsperchunk; i > 0; i-- ) {
      result[currow++] = workspace;
      workspace += blocksperrow;
    }
  }
  return result;
}


/*
   About virtual array management:

   The above "normal" array routines are only used to allocate strip buffers
   (as wide as the image, but just a few rows high).  Full-image-sized buffers
   are handled as "virtual" arrays.  The array is still accessed a strip at a
   time, but the memory manager must save the whole array for repeated
   accesses.  The intended implementation is that there is a strip buffer in
   memory (as high as is possible given the desired memory limit), plus a
   backing file that holds the rest of the array.

   The request_virt_array routines are told the total size of the image and
   the maximum number of rows that will be accessed at once.  The in-memory
   buffer must be at least as large as the maxaccess value.

   The request routines create control blocks but not the in-memory buffers.
   That is postponed until realize_virt_arrays is called.  At that time the
   total amount of space needed is known (approximately, anyway), so free
   memory can be divided up fairly.

   The access_virt_array routines are responsible for making a specific strip
   area accessible (after reading or writing the backing file, if necessary).
   Note that the access routines are told whether the caller intends to modify
   the accessed strip; during a read-only pass this saves having to rewrite
   data to disk.  The access routines are also responsible for pre-zeroing
   any newly accessed rows, if pre-zeroing was requested.

   In current usage, the access requests are usually for nonoverlapping
   strips; that is, successive access start_row numbers differ by exactly
   num_rows = maxaccess.  This means we can get good performance with simple
   buffer dump/reload logic, by making the in-memory buffer be a multiple
   of the access height; then there will never be accesses across bufferload
   boundaries.  The code will still work with overlapping access requests,
   but it doesn't handle bufferload overlaps very efficiently.
*/


METHODDEF( jvirt_sarray_ptr )
request_virt_sarray( j_common_ptr cinfo, int pool_id, wxjpeg_boolean pre_zero,
                     JDIMENSION samplesperrow, JDIMENSION numrows,
                     JDIMENSION maxaccess )
/* Request a virtual 2-D sample array */
{
  my_mem_ptr mem = ( my_mem_ptr ) cinfo->mem;
  jvirt_sarray_ptr result;
  /* Only IMAGE-lifetime virtual arrays are currently supported */
  if( pool_id != JPOOL_IMAGE )
  { ERREXIT1( cinfo, JERR_BAD_POOL_ID, pool_id ); }	/* safety check */
  /* get control block */
  result = ( jvirt_sarray_ptr ) alloc_small( cinfo, pool_id,
           SIZEOF( struct jvirt_sarray_control ) );
  result->mem_buffer = NULL;	/* marks array not yet realized */
  result->rows_in_array = numrows;
  result->samplesperrow = samplesperrow;
  result->maxaccess = maxaccess;
  result->pre_zero = pre_zero;
  result->b_s_open = FALSE;	/* no associated backing-store object */
  result->next = mem->virt_sarray_list; /* add to list of virtual arrays */
  mem->virt_sarray_list = result;
  return result;
}


METHODDEF( jvirt_barray_ptr )
request_virt_barray( j_common_ptr cinfo, int pool_id, wxjpeg_boolean pre_zero,
                     JDIMENSION blocksperrow, JDIMENSION numrows,
                     JDIMENSION maxaccess )
/* Request a virtual 2-D coefficient-block array */
{
  my_mem_ptr mem = ( my_mem_ptr ) cinfo->mem;
  jvirt_barray_ptr result;
  /* Only IMAGE-lifetime virtual arrays are currently supported */
  if( pool_id != JPOOL_IMAGE )
  { ERREXIT1( cinfo, JERR_BAD_POOL_ID, pool_id ); }	/* safety check */
  /* get control block */
  result = ( jvirt_barray_ptr ) alloc_small( cinfo, pool_id,
           SIZEOF( struct jvirt_barray_control ) );
  result->mem_buffer = NULL;	/* marks array not yet realized */
  result->rows_in_array = numrows;
  result->blocksperrow = blocksperrow;
  result->maxaccess = maxaccess;
  result->pre_zero = pre_zero;
  result->b_s_open = FALSE;	/* no associated backing-store object */
  result->next = mem->virt_barray_list; /* add to list of virtual arrays */
  mem->virt_barray_list = result;
  return result;
}


METHODDEF( void )
realize_virt_arrays( j_common_ptr cinfo )
/* Allocate the in-memory buffers for any unrealized virtual arrays */
{
  my_mem_ptr mem = ( my_mem_ptr ) cinfo->mem;
  long space_per_minheight, maximum_space, avail_mem;
  long minheights, max_minheights;
  jvirt_sarray_ptr sptr;
  jvirt_barray_ptr bptr;
  /* Compute the minimum space needed (maxaccess rows in each buffer)
     and the maximum space needed (full image height in each buffer).
     These may be of use to the system-dependent jpeg_mem_available routine.
  */
  space_per_minheight = 0;
  maximum_space = 0;
  for( sptr = mem->virt_sarray_list; sptr != NULL; sptr = sptr->next ) {
    if( sptr->mem_buffer == NULL ) { /* if not realized yet */
      space_per_minheight += ( long ) sptr->maxaccess *
                             ( long ) sptr->samplesperrow * SIZEOF( JSAMPLE );
      maximum_space += ( long ) sptr->rows_in_array *
                       ( long ) sptr->samplesperrow * SIZEOF( JSAMPLE );
    }
  }
  for( bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next ) {
    if( bptr->mem_buffer == NULL ) { /* if not realized yet */
      space_per_minheight += ( long ) bptr->maxaccess *
                             ( long ) bptr->blocksperrow * SIZEOF( JBLOCK );
      maximum_space += ( long ) bptr->rows_in_array *
                       ( long ) bptr->blocksperrow * SIZEOF( JBLOCK );
    }
  }
  if( space_per_minheight <= 0 )
  { return; }			/* no unrealized arrays, no work */
  /* Determine amount of memory to actually use; this is system-dependent. */
  avail_mem = jpeg_mem_available( cinfo, space_per_minheight, maximum_space,
                                  mem->total_space_allocated );
  /* If the maximum space needed is available, make all the buffers full
     height; otherwise parcel it out with the same number of minheights
     in each buffer.
  */
  if( avail_mem >= maximum_space )
  { max_minheights = 1000000000L; }
  else {
    max_minheights = avail_mem / space_per_minheight;
    /* If there doesn't seem to be enough space, try to get the minimum
       anyway.  This allows a "stub" implementation of jpeg_mem_available().
    */
    if( max_minheights <= 0 )
    { max_minheights = 1; }
  }
  /* Allocate the in-memory buffers and initialize backing store as needed. */
  for( sptr = mem->virt_sarray_list; sptr != NULL; sptr = sptr->next ) {
    if( sptr->mem_buffer == NULL ) { /* if not realized yet */
      minheights = ( ( long ) sptr->rows_in_array - 1L ) / sptr->maxaccess + 1L;
      if( minheights <= max_minheights ) {
        /* This buffer fits in memory */
        sptr->rows_in_mem = sptr->rows_in_array;
      } else {
        /* It doesn't fit in memory, create backing store. */
        sptr->rows_in_mem = ( JDIMENSION )( max_minheights * sptr->maxaccess );
        jpeg_open_backing_store( cinfo, & sptr->b_s_info,
                                 ( long ) sptr->rows_in_array *
                                 ( long ) sptr->samplesperrow *
                                 ( long ) SIZEOF( JSAMPLE ) );
        sptr->b_s_open = TRUE;
      }
      sptr->mem_buffer = alloc_sarray( cinfo, JPOOL_IMAGE,
                                       sptr->samplesperrow, sptr->rows_in_mem );
      sptr->rowsperchunk = mem->last_rowsperchunk;
      sptr->cur_start_row = 0;
      sptr->first_undef_row = 0;
      sptr->dirty = FALSE;
    }
  }
  for( bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next ) {
    if( bptr->mem_buffer == NULL ) { /* if not realized yet */
      minheights = ( ( long ) bptr->rows_in_array - 1L ) / bptr->maxaccess + 1L;
      if( minheights <= max_minheights ) {
        /* This buffer fits in memory */
        bptr->rows_in_mem = bptr->rows_in_array;
      } else {
        /* It doesn't fit in memory, create backing store. */
        bptr->rows_in_mem = ( JDIMENSION )( max_minheights * bptr->maxaccess );
        jpeg_open_backing_store( cinfo, & bptr->b_s_info,
                                 ( long ) bptr->rows_in_array *
                                 ( long ) bptr->blocksperrow *
                                 ( long ) SIZEOF( JBLOCK ) );
        bptr->b_s_open = TRUE;
      }
      bptr->mem_buffer = alloc_barray( cinfo, JPOOL_IMAGE,
                                       bptr->blocksperrow, bptr->rows_in_mem );
      bptr->rowsperchunk = mem->last_rowsperchunk;
      bptr->cur_start_row = 0;
      bptr->first_undef_row = 0;
      bptr->dirty = FALSE;
    }
  }
}

static void do_sarray_io( j_common_ptr cinfo, jvirt_sarray_ptr ptr, wxjpeg_boolean writing ) {
  long bytesperrow, file_offset, byte_count, rows, thisrow, i;
  bytesperrow = ( long ) ptr->samplesperrow * SIZEOF( JSAMPLE );
  file_offset = ptr->cur_start_row * bytesperrow;
  /* Loop to read or write each allocation chunk in mem_buffer */
  for( i = 0; i < ( long ) ptr->rows_in_mem; i += ptr->rowsperchunk ) {
    /* One chunk, but check for short chunk at end of buffer */
    rows = MIN( ( long ) ptr->rowsperchunk, ( long ) ptr->rows_in_mem - i );
    /* Transfer no more than is currently defined */
    thisrow = ( long ) ptr->cur_start_row + i;
    rows = MIN( rows, ( long ) ptr->first_undef_row - thisrow );
    /* Transfer no more than fits in file */
    rows = MIN( rows, ( long ) ptr->rows_in_array - thisrow );
    if( rows <= 0 )		/* this chunk might be past end of file! */
    { break; }
    byte_count = rows * bytesperrow;
    if( writing )
      ( *ptr->b_s_info.write_backing_store )( cinfo, & ptr->b_s_info,
                                              ( void FAR * ) ptr->mem_buffer[i],
                                              file_offset, byte_count );
    else
      ( *ptr->b_s_info.read_backing_store )( cinfo, & ptr->b_s_info,
                                             ( void FAR * ) ptr->mem_buffer[i],
                                             file_offset, byte_count );
    file_offset += byte_count;
  }
}

static void do_barray_io( j_common_ptr cinfo, jvirt_barray_ptr ptr, wxjpeg_boolean writing ) {
  long bytesperrow, file_offset, byte_count, rows, thisrow, i;
  bytesperrow = ( long ) ptr->blocksperrow * SIZEOF( JBLOCK );
  file_offset = ptr->cur_start_row * bytesperrow;
  /* Loop to read or write each allocation chunk in mem_buffer */
  for( i = 0; i < ( long ) ptr->rows_in_mem; i += ptr->rowsperchunk ) {
    /* One chunk, but check for short chunk at end of buffer */
    rows = MIN( ( long ) ptr->rowsperchunk, ( long ) ptr->rows_in_mem - i );
    /* Transfer no more than is currently defined */
    thisrow = ( long ) ptr->cur_start_row + i;
    rows = MIN( rows, ( long ) ptr->first_undef_row - thisrow );
    /* Transfer no more than fits in file */
    rows = MIN( rows, ( long ) ptr->rows_in_array - thisrow );
    if( rows <= 0 )		/* this chunk might be past end of file! */
    { break; }
    byte_count = rows * bytesperrow;
    if( writing )
      ( *ptr->b_s_info.write_backing_store )( cinfo, & ptr->b_s_info,
                                              ( void FAR * ) ptr->mem_buffer[i],
                                              file_offset, byte_count );
    else
      ( *ptr->b_s_info.read_backing_store )( cinfo, & ptr->b_s_info,
                                             ( void FAR * ) ptr->mem_buffer[i],
                                             file_offset, byte_count );
    file_offset += byte_count;
  }
}


METHODDEF( JSAMPARRAY )
access_virt_sarray( j_common_ptr cinfo, jvirt_sarray_ptr ptr,
                    JDIMENSION start_row, JDIMENSION num_rows,
                    wxjpeg_boolean writable )
/* Access the part of a virtual sample array starting at start_row */
/* and extending for num_rows rows.  writable is true if  */
/* caller intends to modify the accessed area. */
{
  JDIMENSION end_row = start_row + num_rows;
  JDIMENSION undef_row;
  /* debugging check */
  if( end_row > ptr->rows_in_array || num_rows > ptr->maxaccess ||
      ptr->mem_buffer == NULL )
  { ERREXIT( cinfo, JERR_BAD_VIRTUAL_ACCESS ); }
  /* Make the desired part of the virtual array accessible */
  if( start_row < ptr->cur_start_row ||
      end_row > ptr->cur_start_row + ptr->rows_in_mem ) {
    if( ! ptr->b_s_open )
    { ERREXIT( cinfo, JERR_VIRTUAL_BUG ); }
    /* Flush old buffer contents if necessary */
    if( ptr->dirty ) {
      do_sarray_io( cinfo, ptr, TRUE );
      ptr->dirty = FALSE;
    }
    /* Decide what part of virtual array to access.
       Algorithm: if target address > current window, assume forward scan,
       load starting at target address.  If target address < current window,
       assume backward scan, load so that target area is top of window.
       Note that when switching from forward write to forward read, will have
       start_row = 0, so the limiting case applies and we load from 0 anyway.
    */
    if( start_row > ptr->cur_start_row ) {
      ptr->cur_start_row = start_row;
    } else {
      /* use long arithmetic here to avoid overflow & unsigned problems */
      long ltemp;
      ltemp = ( long ) end_row - ( long ) ptr->rows_in_mem;
      if( ltemp < 0 )
      { ltemp = 0; }		/* don't fall off front end of file */
      ptr->cur_start_row = ( JDIMENSION ) ltemp;
    }
    /* Read in the selected part of the array.
       During the initial write pass, we will do no actual read
       because the selected part is all undefined.
    */
    do_sarray_io( cinfo, ptr, FALSE );
  }
  /* Ensure the accessed part of the array is defined; prezero if needed.
     To improve locality of access, we only prezero the part of the array
     that the caller is about to access, not the entire in-memory array.
  */
  if( ptr->first_undef_row < end_row ) {
    if( ptr->first_undef_row < start_row ) {
      if( writable )		/* writer skipped over a section of array */
      { ERREXIT( cinfo, JERR_BAD_VIRTUAL_ACCESS ); }
      undef_row = start_row;	/* but reader is allowed to read ahead */
    } else {
      undef_row = ptr->first_undef_row;
    }
    if( writable )
    { ptr->first_undef_row = end_row; }
    if( ptr->pre_zero ) {
      size_t bytesperrow = ( size_t ) ptr->samplesperrow * SIZEOF( JSAMPLE );
      undef_row -= ptr->cur_start_row; /* make indexes relative to buffer */
      end_row -= ptr->cur_start_row;
      while( undef_row < end_row ) {
        jzero_far( ( void FAR * ) ptr->mem_buffer[undef_row], bytesperrow );
        undef_row++;
      }
    } else {
      if( ! writable )		/* reader looking at undefined data */
      { ERREXIT( cinfo, JERR_BAD_VIRTUAL_ACCESS ); }
    }
  }
  /* Flag the buffer dirty if caller will write in it */
  if( writable )
  { ptr->dirty = TRUE; }
  /* Return address of proper part of the buffer */
  return ptr->mem_buffer + ( start_row - ptr->cur_start_row );
}


METHODDEF( JBLOCKARRAY )
access_virt_barray( j_common_ptr cinfo, jvirt_barray_ptr ptr,
                    JDIMENSION start_row, JDIMENSION num_rows,
                    wxjpeg_boolean writable )
/* Access the part of a virtual block array starting at start_row */
/* and extending for num_rows rows.  writable is true if  */
/* caller intends to modify the accessed area. */
{
  JDIMENSION end_row = start_row + num_rows;
  JDIMENSION undef_row;
  /* debugging check */
  if( end_row > ptr->rows_in_array || num_rows > ptr->maxaccess ||
      ptr->mem_buffer == NULL )
  { ERREXIT( cinfo, JERR_BAD_VIRTUAL_ACCESS ); }
  /* Make the desired part of the virtual array accessible */
  if( start_row < ptr->cur_start_row ||
      end_row > ptr->cur_start_row + ptr->rows_in_mem ) {
    if( ! ptr->b_s_open )
    { ERREXIT( cinfo, JERR_VIRTUAL_BUG ); }
    /* Flush old buffer contents if necessary */
    if( ptr->dirty ) {
      do_barray_io( cinfo, ptr, TRUE );
      ptr->dirty = FALSE;
    }
    /* Decide what part of virtual array to access.
       Algorithm: if target address > current window, assume forward scan,
       load starting at target address.  If target address < current window,
       assume backward scan, load so that target area is top of window.
       Note that when switching from forward write to forward read, will have
       start_row = 0, so the limiting case applies and we load from 0 anyway.
    */
    if( start_row > ptr->cur_start_row ) {
      ptr->cur_start_row = start_row;
    } else {
      /* use long arithmetic here to avoid overflow & unsigned problems */
      long ltemp;
      ltemp = ( long ) end_row - ( long ) ptr->rows_in_mem;
      if( ltemp < 0 )
      { ltemp = 0; }		/* don't fall off front end of file */
      ptr->cur_start_row = ( JDIMENSION ) ltemp;
    }
    /* Read in the selected part of the array.
       During the initial write pass, we will do no actual read
       because the selected part is all undefined.
    */
    do_barray_io( cinfo, ptr, FALSE );
  }
  /* Ensure the accessed part of the array is defined; prezero if needed.
     To improve locality of access, we only prezero the part of the array
     that the caller is about to access, not the entire in-memory array.
  */
  if( ptr->first_undef_row < end_row ) {
    if( ptr->first_undef_row < start_row ) {
      if( writable )		/* writer skipped over a section of array */
      { ERREXIT( cinfo, JERR_BAD_VIRTUAL_ACCESS ); }
      undef_row = start_row;	/* but reader is allowed to read ahead */
    } else {
      undef_row = ptr->first_undef_row;
    }
    if( writable )
    { ptr->first_undef_row = end_row; }
    if( ptr->pre_zero ) {
      size_t bytesperrow = ( size_t ) ptr->blocksperrow * SIZEOF( JBLOCK );
      undef_row -= ptr->cur_start_row; /* make indexes relative to buffer */
      end_row -= ptr->cur_start_row;
      while( undef_row < end_row ) {
        jzero_far( ( void FAR * ) ptr->mem_buffer[undef_row], bytesperrow );
        undef_row++;
      }
    } else {
      if( ! writable )		/* reader looking at undefined data */
      { ERREXIT( cinfo, JERR_BAD_VIRTUAL_ACCESS ); }
    }
  }
  /* Flag the buffer dirty if caller will write in it */
  if( writable )
  { ptr->dirty = TRUE; }
  /* Return address of proper part of the buffer */
  return ptr->mem_buffer + ( start_row - ptr->cur_start_row );
}


/*
   Release all objects belonging to a specified pool.
*/

METHODDEF( void )
free_pool( j_common_ptr cinfo, int pool_id ) {
  my_mem_ptr mem = ( my_mem_ptr ) cinfo->mem;
  small_pool_ptr shdr_ptr;
  large_pool_ptr lhdr_ptr;
  size_t space_freed;
  if( pool_id < 0 || pool_id >= JPOOL_NUMPOOLS )
  { ERREXIT1( cinfo, JERR_BAD_POOL_ID, pool_id ); }	/* safety check */
  #ifdef MEM_STATS
  if( cinfo->err->trace_level > 1 )
  { print_mem_stats( cinfo, pool_id ); } /* print pool's memory usage statistics */
  #endif
  /* If freeing IMAGE pool, close any virtual arrays first */
  if( pool_id == JPOOL_IMAGE ) {
    jvirt_sarray_ptr sptr;
    jvirt_barray_ptr bptr;
    for( sptr = mem->virt_sarray_list; sptr != NULL; sptr = sptr->next ) {
      if( sptr->b_s_open ) {	/* there may be no backing store */
        sptr->b_s_open = FALSE;	/* prevent recursive close if error */
        ( *sptr->b_s_info.close_backing_store )( cinfo, & sptr->b_s_info );
      }
    }
    mem->virt_sarray_list = NULL;
    for( bptr = mem->virt_barray_list; bptr != NULL; bptr = bptr->next ) {
      if( bptr->b_s_open ) {	/* there may be no backing store */
        bptr->b_s_open = FALSE;	/* prevent recursive close if error */
        ( *bptr->b_s_info.close_backing_store )( cinfo, & bptr->b_s_info );
      }
    }
    mem->virt_barray_list = NULL;
  }
  /* Release large objects */
  lhdr_ptr = mem->large_list[pool_id];
  mem->large_list[pool_id] = NULL;
  while( lhdr_ptr != NULL ) {
    large_pool_ptr next_lhdr_ptr = lhdr_ptr->hdr.next;
    space_freed = lhdr_ptr->hdr.bytes_used +
                  lhdr_ptr->hdr.bytes_left +
                  SIZEOF( large_pool_hdr );
    jpeg_free_large( cinfo, ( void FAR * ) lhdr_ptr, space_freed );
    mem->total_space_allocated -= space_freed;
    lhdr_ptr = next_lhdr_ptr;
  }
  /* Release small objects */
  shdr_ptr = mem->small_list[pool_id];
  mem->small_list[pool_id] = NULL;
  while( shdr_ptr != NULL ) {
    small_pool_ptr next_shdr_ptr = shdr_ptr->hdr.next;
    space_freed = shdr_ptr->hdr.bytes_used +
                  shdr_ptr->hdr.bytes_left +
                  SIZEOF( small_pool_hdr );
    jpeg_free_small( cinfo, ( void * ) shdr_ptr, space_freed );
    mem->total_space_allocated -= space_freed;
    shdr_ptr = next_shdr_ptr;
  }
}


/*
   Close up shop entirely.
   Note that this cannot be called unless cinfo->mem is non-NULL.
*/

METHODDEF( void )
self_destruct( j_common_ptr cinfo ) {
  int pool;
  /* Close all backing store, release all memory.
     Releasing pools in reverse order might help avoid fragmentation
     with some (brain-damaged) malloc libraries.
  */
  for( pool = JPOOL_NUMPOOLS - 1; pool >= JPOOL_PERMANENT; pool-- ) {
    free_pool( cinfo, pool );
  }
  /* Release the memory manager control block too. */
  jpeg_free_small( cinfo, ( void * ) cinfo->mem, SIZEOF( my_memory_mgr ) );
  cinfo->mem = NULL;		/* ensures I will be called only once */
  jpeg_mem_term( cinfo );		/* system-dependent cleanup */
}

void jinit_memory_mgr( j_common_ptr cinfo ) {
  my_mem_ptr mem;
  long max_to_use;
  int pool;
  size_t test_mac;
  cinfo->mem = NULL;		/* for safety if init fails */
  if( ( SIZEOF( ALIGN_TYPE ) & ( SIZEOF( ALIGN_TYPE ) - 1 ) ) != 0 )
  { ERREXIT( cinfo, JERR_BAD_ALIGN_TYPE ); }
  test_mac = ( size_t ) MAX_ALLOC_CHUNK;
  if( ( long ) test_mac != MAX_ALLOC_CHUNK ||
      ( MAX_ALLOC_CHUNK % SIZEOF( ALIGN_TYPE ) ) != 0 )
  { ERREXIT( cinfo, JERR_BAD_ALLOC_CHUNK ); }
  max_to_use = jpeg_mem_init( cinfo ); /* system-dependent initialization */
  /* Attempt to allocate memory manager's control block */
  mem = ( my_mem_ptr ) jpeg_get_small( cinfo, SIZEOF( my_memory_mgr ) );
  if( mem == NULL ) {
    jpeg_mem_term( cinfo );	/* system-dependent cleanup */
    ERREXIT1( cinfo, JERR_OUT_OF_MEMORY, 0 );
  }
  /* OK, fill in the method pointers */
  mem->pub.alloc_small = alloc_small;
  mem->pub.alloc_large = alloc_large;
  mem->pub.alloc_sarray = alloc_sarray;
  mem->pub.alloc_barray = alloc_barray;
  mem->pub.request_virt_sarray = request_virt_sarray;
  mem->pub.request_virt_barray = request_virt_barray;
  mem->pub.realize_virt_arrays = realize_virt_arrays;
  mem->pub.access_virt_sarray = access_virt_sarray;
  mem->pub.access_virt_barray = access_virt_barray;
  mem->pub.free_pool = free_pool;
  mem->pub.self_destruct = self_destruct;
  /* Make MAX_ALLOC_CHUNK accessible to other modules */
  mem->pub.max_alloc_chunk = MAX_ALLOC_CHUNK;
  /* Initialize working state */
  mem->pub.max_memory_to_use = max_to_use;
  for( pool = JPOOL_NUMPOOLS - 1; pool >= JPOOL_PERMANENT; pool-- ) {
    mem->small_list[pool] = NULL;
    mem->large_list[pool] = NULL;
  }
  mem->virt_sarray_list = NULL;
  mem->virt_barray_list = NULL;
  mem->total_space_allocated = SIZEOF( my_memory_mgr );
  /* Declare ourselves open for business */
  cinfo->mem = & mem->pub;
  /* Check for an environment variable JPEGMEM; if found, override the
     default max_memory setting from jpeg_mem_init.  Note that the
     surrounding application may again override this value.
     If your system doesn't support getenv(), define NO_GETENV to disable
     this feature.
  */
  #ifndef NO_GETENV
  {
    char * memenv;
    if( ( memenv = getenv( "JPEGMEM" ) ) != NULL ) {
      char ch = 'x';
      if( sscanf( memenv, "%ld%c", &max_to_use, &ch ) > 0 ) {
        if( ch == 'm' || ch == 'M' )
        { max_to_use *= 1000L; }
        mem->pub.max_memory_to_use = max_to_use * 1000L;
      }
    }
  }
  #endif
}
